"This has become one of their themes," she told Kimmel. "Make sure I'm alive."

BY Lisa Lerer

Hillary Clinton is pushing back against charges that she's physically unfit for the White House.

The Democratic presidential candidate said the accusations are part of a "wacky strategy" by GOP rival Donald Trump and an "alternative reality" that's not focused on the kinds of issues that are most important to voters.

"I do feel sometimes like this campaign has entered into an alternative universe," she said in an appearance on ABC's "Jimmy Kimmel Live" taped Monday afternoon. "I have to step into the alternative reality and, you know, answer questions about, am I alive, how much longer will I be alive, and the like."

Clinton said she doesn't question Trump's health — she believes he's "healthy as a horse."

"This has become one of their themes," she said. "Make sure I'm alive."

The comments marked the first time Clinton has addressed debunked rumors about her health, which have been encouraged by Trump and his backers.

Much of the speculation stems from a concussion Clinton sustained in December 2012 after fainting, an episode her doctor has attributed to a stomach virus and dehydration.

Former New York Mayor Rudy Giuliani urged voters to "go online and put down 'Hillary Clinton illness,'" in an interview with Fox News on Sunday, saying the next morning that she "looks sick." Trump has questioned her stamina at campaign rallies and speeches, saying in a foreign policy address earlier this month that she "lacks the mental and physical stamina to take on ISIS".

Meanwhile, Clinton expressed little concern Monday about the planned release of 15,000 additional State Department emails that went previously undisclosed during an FBI investigation into her use of a private server as secretary of state. The messages could become public in mid-October, just weeks before Election Day.

"My emails are so boring," she told Kimmel. "We've already released 30,000 plus, so what's a few more?"

She joked about photos showing her husband, former President Bill Clinton, smiling and looking overjoyed to be surrounded by the balloons that fell at the end of the Democratic National Convention.

"We were all pretty excited about the balloons," she said. "That's one of the things I enjoy about my husband is that he enjoys so many things and balloons is one of them."

When asked about her preparations for the three debates with Trump, Clinton said she's taking the match-up seriously but is getting ready for "wacky stuff."